You might be able to use a DIO to output a PWM signal, then read that signal with the arduino. (Or if you can spare a PWM port, you could use that). This would give you many more options for colors without tying up a bunch of outputs.
Here is some code to read PWM with the arduino (I haven't tried it, but I have done something similar with an adruino).
https://gist.github.com/ivarvong/8202180
For the labview code you can probably use Pulse.vi. (Page 22-4 in this document, the newer version of labview should have an equivalent vi:
http://www.ni.com/pdf/manuals/372668d.pdf).